This invention relates to an automatic clutch to be disposed between driving and driven members to connect and disconnect the two.
The all-wheel drive employed by certain automobiles and the like is an effective system for making full use of the driving power and braking force of the engine when the vehicle runs on snow-laden and frozen roads, paths in hills, wastelands, or other rough terrain. On ordinary roads, however, the all-wheel driven vehicle would involve the operation of the extra drive-shaft power train and hence produce wasteful consumption of energy and added running noise. For these reasons a special clutch, i.e., free-wheel hub is in use which disconnects the unnecessary drive-shaft system not only from the driving side but also from the road wheel side. To actuate the free-wheel hub, the driver usually must stop the vehicle, go to the vicinity of each wheel equipped with such a hub, and then shift such hub position by hand. In attempts to obviate the inconvenience, devices designed for automatic rather than manual control have been developed in recent years. Nevertheless, they still have shortcomings in that the engine brake will not work, the construction is relatively complex, or the mechanism has to be actuated whenever the vehicle stops. In light of this, we previously developed an automatic clutch which required no manipulation by the driver outside of his vehicle and permits rapid and simple shifting, without any of the disadvantages described above (copending Japanese Patent Application No. 30332/1978, U.S. patent application Ser. No. 916,144, and Canadian Patent Application No. 318,968). However, that automatic clutch sometimes applies an excessive load on part of its structural members due to inadequate timing of engagement, and it was found that, when used in applications where a powerful torque was to be transmitted, the clutch could pose durability problems abut its components.
The automatic clutch in question is constructed as shown in FIG. 15. An annular inner cam a has cam teeth projecting toward a drive clutch b and is secured to the car body with a nuckle i. The drive clutch b has teeth on both sides and is fitted with a sleeve m on a drive shaft f by splines in such a manner that it can rotate with, and slide axially of, the shaft. It is normally biased by a spring r in the declutching direction (rightwardly as shown). A driven clutch d is splined on the outer surface for sliding contact with a housing g and is normally biased by a spring n toward the drive clutch b. When the corresponding teeth of the inner cam a and the drive clutch b are in mesh, the teeth t on the opposite side of the drive clutch and that of the driven clutch e are out of mesh. Conversely, when the inner cam a and the drive clutch b are disengaged onto the teeth (flattened cam projections or lands) of each other, the teeth t of the drive clutch b and the teeth e of the driven clutch d are in mesh. A holdout ring j is fitted slidably on the outer periphery of the drive clutch b. Along its edge the ring has projections adapted to engage the inner cam a. The lower half of FIG. 15 illustrates the automatic clutch in the declutched state. The drive clutch b and the driven clutch d are out of mesh, cutting off the drive. The upper half of the figure shows the clutch engaged, with the rotation of the drive shaft f being transmitted through the sleeve m, drive clutch b, driven clutch d, housing g, and hub s to the road wheel.
In the previously proposed automatic clutch of the construction just described, the inner cam a and the drive clutch b are directly engaged, and therefore, when they are half out of mesh, with their teeth half atop each other, the teeth t on the other side of the drive clutch b may sometimes come half into mesh with the teeth e of the driven clutch d. When this happens, the torque from the drive shaft f is transmitted through the drive clutch b to the driven clutch d. Consequently, the torque is applied to the splined connecting part h between the driven clutch d and the housing g. The inner cam a exerting its force in the clutching direction is then subjected to a heavy load, and hence the connector (e.g., a key in a keyway) between the nuckle i and the inner cam a will be under a heavy load. When the automatic clutch is used in applications where a powerful torque is to be transmitted, the connector will present a durability problem, sometimes breaking down under the burden it must carry.